Delivery vehicles for pressurized fuel and other liquids, such as liquefied petroleum gas (LPG), propane, butane, and so on, typically include a large holding tank located rearwardly of the cab. A fuel sending unit is typically mounted at the center of the tank above eye level of the observer. The sending unit includes a float that rides on the surface of the liquid. The float is connected to a pivoting float arm which is in turn connected to the lower end of a driven shaft that rotates about its axis in response to float movement. A driving magnet is typically located at the upper end of the driven shaft that magnetically couples with a driven magnet inside the gauge head, which is associated with an indicator, so that rotational movement of the driving magnet in response to float movement induces the driven magnet to rotate a proportional amount and rotate the indicator across a scale associated with the gauge head, to thereby display a liquid level condition of the tank to an observer.
When such fuel gauges are mounted to large storage tanks associated with transportation vehicles, such as propane delivery trucks, the gauge head is typically mounted at the rear center of the tank to minimize errors in reading. However, such a location is usually above the operator's field of view, which makes it hard to accurately read the gauge due to parallax errors that occur when the eyes of an observer are not properly aligned with the indicator and scale.
In addition, such gauges also inconvenience an operator since the liquid level within the tank is not readily apparent unless the vehicle is parked on a level surface and the operator exits the cab and walks to the rear of the vehicle to observe the gauge reading. Even when the gauge reading can be manually observed, it may not be accurate within acceptable limits unless compensation of liquid level or volume is manually calculated based on the specific gravity of the particular liquid within the tank, which can be affected by temperature. Accordingly, an operator must have knowledge of the contents of the tank, its specific gravity at a set temperature, and expansion or contraction of the volume based on changes in specific gravity for a particular fluid at different temperatures. Consequently, obtaining a clear and accurate reading of the volume or level of liquid within such storage tanks can be both a difficult and time-consuming task.
It would therefore be desirous to provide a simple, straight forward solution that would reduce or eliminate parallax reading errors while avoiding high development and manufacturing costs associated with redesigning the gauge head, fuel sending unit and/or tank.